1. Technical Field
The present invention relates to an image forming apparatus, particularly to an image forming apparatus using a rolled print medium.
2. Related Art
An image forming apparatus, such as a label printer, performs printing on a print medium having an adhesive surface with no release liner attached thereto, such as adhesive tape or a label sheet with no backing sheet (hereinafter also referred to as a linerless label sheet), and thereafter cuts the print medium into print medium pieces (hereinafter also referred to as label pieces) of a desired length.
A sheet transporting apparatus or image forming apparatus using a rolled sheet (i.e., a print medium wound in a roll) may include, for example, a spool, a transporting device, and a rotational load device. The spool holds a rolled sheet and is rotatable in both a sheet feeding direction and a sheet rewinding direction. The transporting device transports the sheet through an image forming area. The rotational load device places a predetermined rotational load on the spool. Drive force in the sheet feeding direction is not transmitted to the rotational load device, whereas drive force in the sheet rewinding direction is transmitted to the rotational load device.
If the roll is a bonded roll having a core member bonded to an end portion of the print medium, or if the transporting device and other devices in the apparatus are integrated as a single unit drawable from the body of the apparatus, for example, the print medium transported to the transporting device is rewound into the roll as necessary.
Particularly in the case of a roll of print medium having an exposed adhesive surface, such as a linerless label sheet, if the print medium slackens while being rewound into the roll, parts of the adhesive surface may stick together, or the adhesive surface may stick to another component of the apparatus, preventing the medium rewinding operation. It is therefore desirable to apply tension to the print medium during the medium rewinding operation (also referred to as back tension).
A roll of print medium having an adhesive surface may be a face-out roll wound with the rear surface of the adhesive surface facing outward or a face-in roll wound with the adhesive surface facing outward.
Therefore, if the driving of the transporting device and the rotational driving of the spool holding the roll in a sheet feeding device are performed by a single drive source, and if the rotation direction of the spool is different from the winding direction of the roll, it is difficult to apply the back tension to the print medium during the medium rewinding operation. As a result, parts of the adhesive surface may stick together, or the adhesive surface may stick to another component of the apparatus, as described above.